In the rapidly-developing field of wireless communication devices, and in portable electronic devices in general, power supply systems which provide a safe, reliable, long-lasting source of power without compromising the portability of the device are highly desirable. The power supply requirements of many electronic devices are evolving as new generations of integrated circuits are developed which operate at decreasing voltage levels. These decreasing voltage requirements allow battery assemblies for portable electronic devices to be made smaller and lighter. However, the reduction in operating voltages for some chips results in different operating voltage levels for different portions of the electronic device. Further contributing to this problem of multiple supply voltage levels is the fact that analog circuits perform better at voltage levels which are higher than the voltage levels required by many digital integrated circuits. Finally, some circuit components, such as RF power amplifiers and displays, require negative supply voltages. Generating all of the necessary supply voltages for a particular electronic device can consume a significant amount of surface area on a printed circuit board, and is typically inefficient.
An additional problem results from the evolving power supply requirements of mobile telephones and other portable electronic devices, in that devices which require relatively high supply voltage levels experience a relatively insignificant power loss across the contacts which connect the power supply to the device. However, as the voltage supply requirements decrease, the current across the power supply contacts increases, and the voltage drop and power loss across the power supply contacts becomes significant.
Known power supply systems for portable electronic devices use conventional power supply contacts to supply power from a battery assembly to the device. In some cases, multiple power supply contacts are used to decrease the total resistance at the contacts. Different voltage levels can be derived using linear regulators and boost or buck voltage converters. However, known power supply systems do not adequately address the problem of power loss across the power supply contacts. Further, known power supply systems do not adequately address the problems of inefficient use of PC board area, which occurs as a result of multiple linear voltage regulators or boost/buck voltage converters.
One example of a known power supply system is disclosed in U.S. Pat. No. 5,327,065 to Bruni et al. (Bruni). Bruni discloses a hand-held inductive charger having concentric windings for transferring power across a dielectric medium using magnetic induction. More particularly, the charger includes a primary coil and is connected to an electrical power source via a cable. The charger is designed to be inserted into a receptacle housing having a secondary coil coupled to an automobile battery. When the charger is inserted into the receptacle housing, the primary and secondary coils form a transformer which transfers power from the electrical power source to the automobile battery to charge the battery. Since the Bruni device relates to the charging of electric automobile batteries, it is not designed for portability. Further, the Bruni device is designed to transfer approximately 6000 watts, and therefore is not applicable to typical portable electronic devices. Further, Bruni does not adequately address the problem of power loss occurring at the power supply contacts due to the relatively low voltages required by the powered device, and does not address the problem of providing multiple supply voltages.
Another example of a known power supply system is disclosed in U.S. Pat. Nos. 5,157,319 and 5,341,083 to Klontz et al. (Klontz). Klontz discloses a contactless battery charging system for recharging an electric automobile battery. In the Klontz system, a primary converter converts power from a power source into high frequency power, and a secondary converter in the automobile is coupled to the battery. When the primary and secondary converters are coupled together by a contactless coupling to form a transformer, power is transferred from the power source to the battery for charging. As described above with respect to Bruni, Klontz does not address the problem of providing multiple supply voltages to a portable electronic device, or the problem of power consumption across the power supply contacts in a relatively low-voltage portable electronic device.
U.S. Pat. No. 5,264,776 to Hulsey (Hulsey) discloses an inductive coupling charge port for charging an electric vehicle. The Hulsey system includes a hand-held primary coil assembly connected to a power source, and a secondary coil assembly disposed in a cavity in the vehicle. The secondary coil assembly is connected to the vehicle battery, and includes a first portion of a transformer core. A hinged access door provides access to the cavity, and has a second portion of the transformer core attached by a compressible material to the inner surface of the hinged access door. When the primary coil assembly is inserted into the cavity and the hinged access door is closed, a complete transformer core is formed, and power is transferred from the power source to the battery. As with the Bruni and Klontz systems, the Hulsey system is not directed to providing multiple voltages to a portable electronic device.
Therefore, it would be desirable for a power supply system for a portable electronic device to provide a reliable, safe, relatively long-life power supply to the portable electronic device, including multiple supply voltages, in an efficient manner so as to enhance the portability of the electronic device.